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OpenGL ES 1.0 and EGL 1.0 reference manual and man pages (written by
Claude Knaus, based on OpenGL SI man pages).

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook V4.2//EN" "DTD/docbook/docbookx.dtd">

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<refentry id="glDepthRange">
  <refmeta>
    <refentrytitle>glDepthRange</refentrytitle>
    <manvolnum>3G</manvolnum>
  </refmeta>

  <refnamediv>
    <refdescriptor>glDepthRange</refdescriptor>
    <refname>glDepthRangef</refname>
    <refname>glDepthRangex</refname>
    <refpurpose>specify mapping of depth values from normalized
    device coordinates to window coordinates</refpurpose>
  </refnamediv>

  <refsynopsisdiv>
    <title>C Specification</title>

    <funcsynopsis>
      <funcprototype>
        <funcdef>void <function>glDepthRangef</function></funcdef>
        <paramdef>GLclampf <parameter>near</parameter></paramdef>
        <paramdef>GLclampf <parameter>far</parameter></paramdef>
      </funcprototype>
      <funcprototype>
        <funcdef>void <function>glDepthRangex</function></funcdef>
        <paramdef>GLclampx <parameter>near</parameter></paramdef>
        <paramdef>GLclampx <parameter>far</parameter></paramdef>
      </funcprototype>
    </funcsynopsis>
  </refsynopsisdiv>

  <refsect1>
    <title>Parameters</title>

    <variablelist>
      <varlistentry>
        <term>
          <parameter>near</parameter>
        </term>

        <listitem>
          <para>Specifies the mapping of the near clipping plane to
          window coordinates. The initial value is 0.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term>
          <parameter>far</parameter>
        </term>

        <listitem>
          <para>Specifies the mapping of the far clipping plane to
          window coordinates. The initial value is 1.</para>
        </listitem>
      </varlistentry>
    </variablelist>
  </refsect1>

  <refsect1>
    <title>Description</title>

    <para>After clipping and division by <parameter>w</parameter>,
    depth coordinates range from -1 to 1, corresponding to the
    near and far clipping planes. <function>glDepthRange</function>
    specifies a linear mapping of the normalized depth coordinates
    in this range to window depth coordinates. Regardless of the
    actual depth buffer implementation, window coordinate depth
    values are treated as though they range from 0 through 1 (like
    color components). Thus, the values accepted by 
    <function>glDepthRange</function>
    are both clamped to this range before they are accepted.</para>

    <para>The setting of (0, 1) maps the near plane to 0 and the far
    plane to 1. With this mapping, the depth buffer range is fully
    utilized.</para>
  </refsect1>

  <refsect1>
    <title>Notes</title>

    <para>It is not necessary that <parameter>near</parameter> 
    be less than <parameter>far</parameter>.
    Reverse mappings such as 
    <inlineequation><math>
      <mi>near</mi>
      <mo>=</mo>
      <mn>1</mn>
    </math></inlineequation>,
    and 
    <inlineequation><math>
      <mi>far</mi>
      <mo>=</mo>
      <mn>0</mn>
    </math></inlineequation>
    are acceptable.</para>
  </refsect1>

  <refsect1>
    <title>See Also</title>

    <para>
    <citerefentry><refentrytitle>glDepthFunc</refentrytitle></citerefentry>, 
    <citerefentry><refentrytitle>glPolygonOffset</refentrytitle></citerefentry>, 
    <citerefentry><refentrytitle>glViewport</refentrytitle></citerefentry>
    </para>
  </refsect1>
</refentry>